PROCESS FOR REDUCTION OF TIME IN GAS CARBURIZING PROCESS AND COOLING APPARATUS THEREFOR

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the Indian Patent Application number 202443067114, titled “AN IMPROVED PROCESS FOR REDUCTION OF TIME IN GAS CARBURIZING PROCESS AND COOLING APPARATUS THEREFOR,” filed Sep. 5, 2024, the entire disclosure of which is incorporated by reference herein, in its entirety, for all purposes.

BACKGROUND OF THE PRESENT INVENTION

Technical Field of the Present Invention Disclsoure

The subject matter of the present invention relates generally to a process of gas carburization. Particularly and not exclusively, the subject matter of the present invention is related an effective and efficient gas-carburizing process and an apparatus for hardening the surface of a steel part by diffusing hydro-carbons into the surface layer of the steel part.

DESCRIPTION OF THE RELATED ART

In conventional method of gas carburizing process, it requires an atmospheric heat-treating furnace herein called heat treating furnace along with a gas generator for conventional carburizing. However, there are conventional designs that use heat treating furnaces for carburizing without gas generator. Examples of this is a drip feed type furnace with methanol for direct carburizing.

In the conventional method, the process of quenching is a low agitation quenching with low rate of velocity of the flow of quenching oil. Further to this, the time required for carburization process begins from the stage where the temperature is about 930° C. to attain the carburization. The cited art envisages and illustrates the carburization process in stepwise incremental values of temperature from 800° C., 850° C., 900° C. to 930° C. This step wise incremental temperature based process results in the increased time of operation and is found to reduce the efficiency of the process by 20%˜30%.

In the conventional methods, the time required for carburizing starts from 930° C. to attain the carburization. Further to this, in the conventional method the process of quenching takes place with low agitation quenching and oil velocity (rpm),

Accordingly, in order to overcome one or more drawbacks associated with the related art and, to increase and to improve the efficiency with reduced operation time, there exists a need for an improved process for gas carburization wherein the conceived process is characterized by:

• • maintenance of step-wise temperature of the furnace during the carburization process;
  • reduced cost of operation;
  • reduced operation and processing time; and
  • enhanced efficiency.

OBJECTIVES OF THE PRESENT INVENTION DISCLOSURE

Few of the objectives of the present invention are as stated below:

• • an objective of the present invention is to provide an effective and efficient process for gas carburization at constant temperature wherein step-wise furnace temperature is maintained throughout the carburization process;
  • another objective of the present invention is to provide an effective and efficient process for gas carburization which has reduced cost of operation;
  • yet another objective of the present is to provide an effective and efficient process for gas carburization which has reduced operation and processing time; and
  • an additional objective of the present invention is to provide an effective process for gas carburization which has increased efficiency.

Other objectives, aspects, features and goals of the present invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION DISCLOSURE

Summary of the Present Invention

In order to obviate the shortcomings of the related art, an effective and efficient improved process for gas carburization at constant temperature is illustrated herein.

Principally, in accordance with an aspect of the present invention, the process for reduction of time in gas carburizing process, includes the steps of: placing a part into an atmospheric carburizing furnace; maintaining the step-wise temperature of the carburizing furnace during the heating of the part in the carburizing furnace; heating the part at the first pre-set temperature of 800° C. for the duration of 10 minute while adding a hydrocarbon gas into the carburizing furnace; heating the part at the second pre-set temperature of 850° C. for the duration of 10 minute while adding the hydrocarbon gas along with methanol into the carburizing furnace; heating the part at the third pre-set temperature of 900° C. for the duration of 10 minute while adding the hydrocarbon gas into the carburizing furnace; and based on the requirement of the depth, heating the part at the fourth pre-set temperature of 930° C. for a duration of variable time and for variable carbon potential in accordance with the requirement by adding the hydrocarbon gas into the carburizing furnace; heating the part at the fifth pre-set temperature of 940° C. for a duration of variable time and for variable carbon potential in accordance with the requirement by adding the hydrocarbon gas into the carburizing furnace; heating the part at the sixth pre-set temperature of 965° C. for a duration of variable time and for variable carbon potential in accordance with the requirement by adding the hydrocarbon gas into the carburizing furnace, and quenching the part using quenching oil flowing in the quenching oil circulation pipe, wherein the process resulting in reduced processing time and increased efficiency.

Additionally, in accordance with an aspect of the present invention, a cooling apparatus is provided for the process for reduction of time in gas carburizing process. The cooling apparatus includes essentially a quenching chamber, a propeller for agitation, work movement elevator, a work basket, an elevator drive cylinder. There is also provided a quench oil circulation pipe having an input end and exit/output end. The quenching oil is directed to flow through with a pre-set/pre-determined/selected flow rate facilitated by the propeller. There is an agitation motor operably coupled with input end of the quench oil circulation pipe to facilitate the flow of the quenching oil through the circulation pipe and a rectification device to facilitate the equalization of the flow rate of the quenching oil. The cooling apparatus is configured to facilitate homogeneous cooling and to provide improvement in the severity of quench. The cooling apparatus is further configured to function in at least one mode of operation, either manual mode or in an automatic mode.

The following description is illustrative in nature and is not intended to be in any way limiting. In addition to the aforementioned illustrative aspects, embodiments, and features of the present invention, further aspects, embodiments and features will become apparent by reference to the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The non-limiting and non-exhaustive embodiments of the present invention are described with reference to the figures in the accompanying drawings wherein like reference letters and numerals indicate the corresponding parts in various figures unless otherwise specified. It will be appreciated that for simplicity and clarity of illustration, parts and elements illustrated in figures of the drawings have not necessarily been drawn to scale. Further, the accompanying drawings illustrate the best mode for carrying out the invention as presently contemplated and set forth herein after. The present invention may be more clearly understood from a consideration of the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings in which:

FIG. 1 is an illustration of conventional gas carburization process;

FIG. 2 is an illustration of the characteristic of the gas carburization process in accordance with an aspect of the present invention;

FIG. 3 is an illustration of the quench oil cooling apparatus in accordance with another aspect of the present invention; and

FIG. 4 is an illustration of the state of art of gas carburization process in step-wise heating from initial temperature to final temperature in accordance with an aspect of the present invention.

MOST PREFERRED AND ILLUSTRATED EMBODIMENTS

The process of gas carburization as disclosed herein provides a visualization of the advantageous process for reduction of time in gas carburizing process and the cooling apparatus therefor described herein.

Referring now to FIG. 1, the conventional gas carburization process is illustrated. FIG. 1(a) is Fe (Iron) and Carbon phase diagram. The carburizing is performed at a predetermined temperature 930° C. FIG. 1(b) shows a practical heat cycle for carburizing. The part is heated to a predetermined temperature of 930° C. for carburizing in the furnace with the atmosphere. When the part reaches the carburizing temperature 930° C., it confirms that the carburization has started and with diffusion cycle to follow. In conventional methods, it is assumed that carburizing starts at 930° C.

Referring now to FIG. 2, the characteristic of the gas carburization process in accordance with an aspect of the present invention, is illustrated. FIG. 2 illustrates the characteristics of this invention before the parts reach the carburizing temperature at 965° C. The process starts with a step heating from 800° C., 850° C., 900° C. with the part being held at each mentioned temperature for 10 minutes and for varied time and carbon potential at 930° C., 940° C. and 965° C. which are derived as per case depth requirement.

The process for reduction of time in gas carburizing process of the present invention includes the following steps that are characterized by:

• • a) placing a part into an atmospheric carburizing furnace;
  • b) maintaining the step-wise temperature of the carburizing furnace during the heating of the part in the carburizing furnace from 800° C. through 965° C., via 830° C., 850° C., 900° C., 930° C. and 940° C.;
  • c) heating the part at the first pre-set temperature for the duration of pre-set constant time interval while adding a hydrocarbon gas into the carburizing furnace;
  • d) heating the part at the second pre-set temperature for the duration of pre-set constant time interval while adding the hydrocarbon gas along with methanol into the carburizing furnace;
  • e) heating the part at the third pre-set temperature for the duration of pre-set constant time interval while adding the hydrocarbon gas into the carburizing furnace; and
    based on the requirement of the depth,
  • f) heating the part at the fourth pre-set temperature for a duration of variable time and for variable carbon potential in accordance with the requirement by adding the hydrocarbon gas into the carburizing furnace; and
  • g) heating the part at the fifth pre-set temperature for a duration of variable time and for variable carbon potential in accordance with the requirement by adding the hydrocarbon gas into the carburizing furnace;
  • h) heating the part at the sixth pre-set temperature for a duration of variable time and for variable carbon potential in accordance with the requirement by adding the hydrocarbon gas into the carburizing furnace, and
  • i) quenching the part using quenching oil flowing in the quenching oil circulation pipe, wherein the process resulting in reduced processing time and increased efficiency.

In other words, the present invention imparts a process of carburization on a part starting from 800° C. by adding LPG or propane gas into the furnace. This begins the carburizing process. During this period the temperatures are maintained at 800° C., 850° C. and 900° C. for 10 minutes duration. With the rise of temperatures from 800° C., 850° C., 900° C., 930° C. and 965° C. the carburization takes place by the presence of LPG and propane inside the furnace. To allow penetration of saturated carbon content to the surface of the part is done by altering the carbon potential at each set temperature (as above). The apparatus is required to operate in manual or automatic mode a certain quantity of LPG or propane to reach the required carbon potential at the set temperature. As referred to in FIG. 2, the surface carbon content is diffused. As referred to in FIG. 4, the surface carbon content reaches 1.3% at 965° C. more effectively. This shows that the carburization takes place during the step heating of the part.

In accordance with an aspect of the present invention, the pre-set constant time interval is 10 minutes. The hydrocarbon gas is either liquid petroleum gas (LPG) or Propane.

Referring now to FIG. 3, the cooling apparatus/quench oil cooling apparatus is illustrated. The quenching chamber is denoted by the reference numeral 1, the agitation motor is denoted by the reference numeral 2, the propeller used for agitation is denoted by the reference numeral 3, the work movement elevator is denoted by the reference numeral 4, the work basket is denoted by the reference numeral 5, the elevator drive cylinder is denoted by the reference numeral 6, the quench oil circulation pipe is denoted by the reference numeral 7, and the rectification device adapted to facilitate the equalization of the flow rate of the quenching oil is denoted by the reference numeral 8.

In accordance with an additional embodiment of the present invention, quench oil circulation pipe 7 is provided with an input end and exit/output end. The quenching oil is directed to flow through with a pre-set/pre-determined/selected flow rate facilitated by the propeller 3. The agitation motor 2 is operably coupled with input end of the quench oil circulation pipe 7 to facilitate the flow of the quenching oil through the circulation pipe 7. The quenching oil is directed to flow through in a pre-set/pre-determined/selected flow rate facilitated by a propeller 3.

Further to this, the cooling apparatus is configured to facilitate homogeneous cooling and provide further, an improvement in the severity of quench. The cooling apparatus is further configured to function in at least one mode of operation, which is either in a manual mode or in an automatic mode. The characteristic of the present invention is illustrated. In accordance with an aspect of the present invention, the process for gas carburizing includes the step of placing a part in an atmospheric carburizing furnace. The atmospheric carburizing furnace essentially consists of a quenching chamber with a plurality of quenching oil circulation pipes provided therein. Each oil circulation pipe is provided with an input end and exit/output end. The quenching oil is directed to flow through in a pre-set/pre-determined/selected flow rate facilitated by a propeller.

Further to this, the process includes an agitating motor operably coupled with input end of each of the oil circulation pipes. The motor facilitates the flow of the quenching oil through each circulation pipe. There is provided perforated grid having a plurality of unform openings at the exit end of each of the oil circulation pipes. This in turn facilitates the selective increment in the pre-set/pre-determined/selected flow and the quenching oil is directed through the quenching chamber and recirculated.

The revolutions of the motor are changed as referred to in FIG. 3 and severity of quench is measured by increasing the revolutions of the motor, the effectiveness of the cooling is drastically improved. The number of revolutions of the motor knew that the severity of quench became 0.80{circumflex over ( )}-1 at the time of 1,500 rpm.

In addition, distortion level is examined after the heat-treatment by the Navy test specimen. It is noted the severity of the quench in the range from 0.43 to 0.8{circumflex over ( )}-1. did not offer any significant difference in a level of risk of 5% in a range from 0.43 to 0.8{circumflex over ( )}-1.

The test made on the part; we were able to show the quantity of carbon at pre-determined positions to show effective case depth (Hv550) 0.28% from 0.4% (conventional law) by improving severity of quench to 0.43{circumflex over ( )}-1.

The flow rate of the quenching oil in the oil circulation pipe is 1.6 m/s I the disclosed process herein. The rating of the propeller is in the range of about 1200 rpm˜ 1500 rpm. The dimension of each of the plurality of uniform openings in the perforated grid is 100 mm.

Referring now to FIG. 4, a practical example for an effective case depth of 1.5 mm is illustrated.

In contrast to the conventional process, in the present invention, heating is initiated from 780° C. and heated step-wise up to the temperature of 965° C. in duration of 318 minutes. The gas carburizing process of the present invention is found to utilize duration of 240 minutes, with diffusion time of 120 minutes, thereby making the total time duration to be 558 minutes, whereas in the conventional process, heating is initiated from 850° C. to 950° C. in duration of 165 minutes. The gas carburizing process of the conventional method utilizes duration of 675 minutes, with diffusion time of 105 minutes making the total time duration to be 985 minutes. Therefore, the technical advantage and significance of the present invention lies in the fact of 25.91% reduction in time for the gas carburization process. That is to say, the time duration required for the process of gas carburization, in accordance with the present invention is reduced by 255 minutes (or ˜4 hour).

The result obtained using the process of the present invention is tabulated as follows at varied potentials of Carbon Monoxide (CO), Carbon di Oxide (CO₂) and element Carbon (C).

The result of CO, CO₂ and carbon potential

The disclosed process of gas carburization herein, with heating the part at the constant temperature of the furnace, results in the reduced processing time and increased efficiency.

From the foregoing description, it will be seen that the present invention is well adapted to attain all ends and objectives herein above set forth together with other advantages which are obvious, and which are inherent to the structure.

Technical Advantages and Economic Significance

The present invention provides a process for reduction of time in gas carburizing process and cooling apparatus therefore. The invention is characterized by maintenance of step-wise temperature of the furnace during the carburization process, reduced cost of operation, reduced operation and processing time, and enhanced efficiency.

While the invention has been described in terms of particular variations and illustrative figures, those of skill in the art will recognize that the invention is not limited to the variations or figures described.

In addition, where methods and steps described above indicate certain events occurring in certain order, those of skill in the art will recognize that the ordering of certain steps may be modified and that such modifications are in accordance with the variations of the invention. Additionally, certain steps may be performed concurrently in a parallel process, when possible, as well as performed sequentially as described above. Therefore, to the extent there are variations of the invention, which are within the spirit of the disclosure or equivalent to the inventions found in the claims, it is the intent that this patent will cover those variations as well.